The embodiments herein generally relate to liquid cooled generators and more specifically to improved methods and systems of air bubble flushing in liquid cooled generators.
Liquid cooled generators, such as two-pole generators, may be used in aircraft applications. Such generators employ a cooling flow of fluid through spaces between conductors in a main field winding to prevent overheating and damage to the main field winding. When first installed, or during various maintenance operations, the generators may have air or other gas within or throughout the flow paths designed for the cooling fluid. When the cooling fluid is then pumped into the generator air bubbles may be trapped in various sections of the generators, particularly around the main winding. Such air bubbles may enable overheating and damage to the generator during operation.
As such, flushing of the generator cooling system is performed to remove air from the cooling fluid flow path, and to prevent the air bubbles from remaining in the generator. In order to flush air bubbles from the inlet and exit end turns of the main winding bundle, a cooling tube (bubble flushing tube) may be formed in the axis of the core lamination that forms the core of the winding. During filling with cooling fluid, such as oil, and/or during operation, air bubbles will flow through the bubble flushing tube and exit the generator through a radial shaft orifice downstream of the main winding. In order to flush the air bubbles, such systems divert some of the cooling fluid from the main winding portion and through the central core in order to remove the bubbles from the system.